Digital based electronic media formats are finally on the cusp of largely replacing the older analog electronic media formats. Digital compact discs (CDs) replaced analog vinyl records long ago. Analog magnetic cassette tapes are becoming increasingly rare. Second and third generation digital audio systems such as Mini-discs and MP3 (MPEG Audio—layer 3) are now taking market share from the first generation digital audio format of compact discs.
The domain of video media has been slower to move to digital storage and transmission formats than audio. The slower transition to digital has been largely due to the massive amounts of information required to accurately represent video in digital form. The massive amounts of digital information needed to accurately represent video require very high-capacity digital storage systems and high-bandwidth digital transmission systems.
However, video is now rapidly moving to digital storage and transmission formats. Faster computer processors, high-density storage systems, and new efficient compression and encoding algorithms have finally made digital video practical at consumer price points. The DVD (Digital Versatile Disc), a digital video storage system, has been one of the fastest selling consumer electronic products in years. DVDs have rapidly supplanted Video-Cassette Recorders (VCRs) as the pre-recorded video playback system of choice due their high video quality, very high audio quality, convenience, and wealth of extra features. Furthermore, the antiquated analog NTSC (National Television Standards Committee) video transmission system is now slowly being phased out in favor or the newer digital ATSC (Advanced Television Standards Committee) video transmission system. Direct Broadcast Satellite (DBS) television networks have long been using digital transmission formats in order to conserve precious satellite bandwidth.
Computer systems have been using various different digital video formats for a number of years. Among the best digital video compression and encoding systems used by computer systems have been the digital video compression and encoding systems backed by the Motion Pictures Expert Group that is better known by its acronym “MPEG.” The three most well known and highly used digital video formats from MPEG are known simply as MPEG-1, MPEG-2, and MPEG-4. VideoCDs and low-end consumer-grade digital video editing systems use the relatively primitive MPEG-1 format. Digital Versatile Discs (DVDs) and the Dish Network brand direct broadcast satellite (DBS) television system use the higher-quality MPEG-2 digital video compression and encoding system. The MPEG-4 is rapidly being adapted by new computer based digital video encoders and players.
The MPEG-2 and MPEG-4 standards compress a series of video frames (or fields) and encode the compressed video frames into a digital stream. When encoding a video frame with the MPEG-2 and MPEG-4 systems, a video frame is divided into a rectangular grid of macroblocks. Each macroblock is then independently compressed and encoded.
When compressing the macroblocks from a video frame, an MPEG-2 or MPEG-4 encoder employs a quantizer module that selects a quantizer value (q) that is used to quantize individual numeric values associated with the macroblock. The smaller the quantizer value (q), the more bits will be used to encoded the macroblock. In order to efficiently compress the macroblocks that make up a video frame, the quantizer module must be able to select an appropriate a quantizer value (q). Ideally, the selected quantizer value (q) will maximize the compression of the video frame while ensuring a high quality compressed video frame.